Setting up a server is often required to provide a specific function or service. Most of the time, said services are implemented to centrally manage data, add messaging and collaboration to an enterprise, or establish a web presence on the Internet.
However, most of these services would not be possible without a server running the Dynamic Host Control Protocol (DHCP) -- and DNS, which will be the focus of my next article -- on the LAN, since it manages the pool of IP addresses assigned to network devices and is directly related to getting clients online and communicating.
Setting up DHCP
- Open the Server.app application (Figure A).
- Login to the server management console with an
administrative account (Figure B).
- Click on DHCP under Services to bring up the DHCP management pane (Figure C).
Managing DHCP Networks
You'll notice two tabs, Networks and Clients, with a range of IP addresses created by default when Open Directory is first created. The Networks tab is used to contain a list of IP address range(s) for your specific network. The protocol will automatically assign IP addresses to network-based devices as they go online and request one from DHCP.
- On the Networks tab, use the plus sign [+], minus sign [-], and pencil icon to add, remove, or edit a range listing. Click the plus sign [+] to add a new IP range (Figure
D) with the specific range assigned to your enterprise (Figure E).
- Once all the information has been added, you can
specify the IP address(es) of DNS server(s) in the event that you wish to
assign certain DNS servers to specific IP ranges (for example, managing multiple sites can be addressed by creating a
DHCP range for each site and assigning a specific DNS server IP to each site’s
range, if necessary -- as in Figure F).
- Highlighting a range and clicking the minus sign [-] or pencil icon will remove or allow you to edit that specific IP range.
- Click Done to commit changes to Open Directory, and click the ON/OFF switch to ON to start the DHCP service. *
Managing DHCP Clients
- The Clients tab of the DHCP service pane is
used to manage statically assigned IP addresses to nodes based on the MAC
address on the network card (Figure G).
- Use the plus sign [+], minus sign [-], and pencil icon to add, remove, or edit a static entry. Click the plus sign [+] to add a new static IP
entry by associating the address with the MAC address of the specific device (Figure H).
- Under the Network section, select the DHCP range to associate with the device, and then click Done to commit the changes to DHCP and OD.
* Note: When starting the DHCP service, ensure
that no other conflicting DHCP services are running on the network, as issues
will arise almost immediately and negatively impact all network devices that
are relying on IP addresses to obtain online connectivity. If OS X Server
discovers another potential instance of DHCP running on the LAN, it’ll prompt
you to confirm prior to activating the DHCP service (Figure I).
Dynamically assigning IPs is one of those services that are fundamental to the enterprise. It’s something so simple and lightweight -- yet, without it, medium- to large-scale IT departments would be hard pressed by having to physically keep track of and visit each and every network-capable device and manually configure them. While the process is less cumbersome for small office/home office (SOHO) environments, it steals precious time away from productivity.
DHCP is an infinitely more efficient method of managing addresses and, to a greater extent, managing connectivity at multiple sites by keeping the ranges split up. Coupled with assigned names servers, system access to such resources could be load-balanced or, at the very least, easy to restore in the event of a service outage.
Jesus Vigo is a Network Administrator by day and owner of Mac|Jesus, LLC, specializing in Mac and Windows integration and providing solutions to small- and medium-size businesses. He brings 15 years of experience and multiple certifications from several vendors, including Apple and CompTIA.